Polyester resin, as the term is herein used, designates a linear-type alkyd possessing carbon-to-carbon double bond unsaturation in the polymer chain. These unsaturated polyesters may be crosslinked by reaction with monomers such as styrene or diallyl-phthalate usually in the presence of a peroxide to form insoluble and infusible resins without the formation of a by-product during the curing reaction. These polyester resins possess broad commercial utility due to their versatility and cost effectiveness. Such utility includes in the low-pressure laminating field; in the coating field as attractive and durable finishes for concrete, masonry, wood, plastic, wallboard, and metal; new specialty resins targeted for polymer concrete, mine-bolt resins, transfer molding, restorative dentistry, and the like. As a result of the increased applications, particularly since the polyester resins for many applications must be used outdoors where temperatures cannot be easily controlled, it has become essential to increase the cure rates of such polyester resins at low temperatures without detracting from the physical properties of the resins. While the use of promoters such as the tertiary amines, including dimethylaniline and diethylaniline, in the curing of the unsaturated polyester resins, with a peroxide initiator is known, the effectivenss of such promoters falls off dramatically at low temperatures. While the dimethyltoluidines are known cure promoters, they have not been recognized to have unusual effectiveness at low temperatures.
Accordingly, there is a need for more effective cure promoters which will provide a fast cure at low temperatures without adversely affecting the physical properties of the cured resins.